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Video: Robotic flowers reveal limits of moth's night vision

In order for the hawk moth to feed on nectar, it doesn’t just have to hit a flower’s bull’s-eye; it has to hit it in the dark while the flower sways back and forth. To figure out how the hummingbird-sized insect does this, researchers created robotic flowers that move back and forth at different speeds. Then, using high-speed video, they recorded how well the insects could keep their "tongues" inside the moving flowers at different light levels. From mathematical calculations about how the brain works, the researchers predicted that to make the best of the dark, the moth's brain would need more time to process incoming light—similar to a photographer leaving a shutter open longer—and thus its tracking would lag. Indeed, the video revealed, the moth's tracking response is 17% slower in moonlight compared with dusk, the researchers report online today in Science (and which Sciencefirst reported in 2013). The moth needs to slow its brain to collect enough light to see the flower, but at first it seemed that this adaptation would work against the moth on windy nights. However, the team also filmed flowers from five species frequented by the moth and found they don't move back and forth fast enough for this slower response to be a problem. Knowing how moths deal with these challenges should eventually help engineers design robots that can also respond quickly in low-light conditions, the researchers say.